Difference Between First() and FirstOrDefault() in LINQ

LINQ Is becoming Important Part For Developers..But For New People who Are New To LINQ IS Difficult To Understand Difference Between Many Similar Syntaxes like First() and FirstOrDefault(),Single() and SingleOrDefault() etc.

Here I am going To Explain Difference Between First(0 and FirstOrDefault().

At The Time Of Interview And using LINQ its necessary To Understand Differences Between First() and FirstORDefault().It IS Commonly Used Syntax While Using LINQ().

Here Is Sample Table.

Member

A. First()

1. When we Use First() in LINQ in Query Syntax Or Method Syntax, At that Time If we Do not Get any Record Corresponding To Expression in Where Clause then It Will Throw You Exception as: InvalidOperationException: Sequence contains no elements.
   
   1. Var x=(from m in Member
   2. Where m.UserName=’S000’
   3. Select m.Name,m.Income,m.Year ).First()
   In The Member table There Is no Such Record Which Will Match the expression so Above Query will Throw: InvalidOperationException: Sequence contains no elements.
   
   We Can Handle This Exception In C# by using try Catch like:
   
   1. try
   2. {
   3. Var x=(from m in Member
   4. Where m.UserName=’S000’
   5. Select m.Name,m.Income,m.Year
   6. ).First()
   8. }
   9. catch (InvalidOperationException ex)
   10. {
   11. Console.WriteLine(ex.Message);
   12. }
2. When There Are Multiple Records Releted To TO Matching Expression and If You want only the First One Then You can Use First().
   
   i.e:
   
   1. Var x=(from m in Member
   2. Where m.UserName=’s123’
   3. Select m.Name,m.Income,m.Year).First()
   Then You Will get The Result Like:
   
   

   PQR

   2010-11

   50000

   S123

   
   
3. First() returns First Element Of Sequence.
   
   
4. First() throws Exception when There IS No element Presnt In Table.